#include<stdio.h>
int main(void)
{
    int grade_score,i;

    scanf("%d",&grade_score);

    i=grade_score/10;

    switch (i){
        case 10:
        case 9:
        printf("A");break;
        case 8:
        printf("B");break;
        case 7:
        printf("C");break;
        case 6:
        printf("D");break;
        default:
        printf("E");

    }

    return 0;
}